The consequences of the historical flattening of Philadelphia

My novel-in-progress is set in the Philadelphia area in about one hundred years in the future. For purposes of setting, I wanted to figure out what areas in Philadelphia will be most affected by climate change. I figured the Southern Philadelphia would be the hardest hit, the southernmost part of the area that abuts where the Schuylkill meets the Delaware rivers; also, any place along the Delaware and Schuylkill Rivers. For context, here’s what Philadelphia looks like:

Philadelphia Neighborhoods - Google My Maps

It’s easy to see the Delaware River on this map; the Schuylkill River is a much thinner band of blue on the western side of the city. However, despite the fact that much of the city is bracketed by rivers, when you look at a map at areas that will be inundated by sea level rise over a hundred years (as indicated by the different colors of green), while there are definitely troubles in Southern Philadelphia (the airport is toast, for example) and along the Delaware, most of the city seems to be intact.


I’d thought that the news stories I’d go looking for in about flooding in Philadelphia would relate to these obviously imperiled, low-lying neighborhoods. But what I first happened upon was a story of flooding in a surprising Philadelphia locale.

In Germantown in October 2011, a flash flood resulted in the drowning of a 27-year-old woman after she was trapped in her car by floodwaters. Feet of floodwater invaded neighboring homes and businesses.

On a semi-regular basis, residents of Germantown deal with an influx of sewage in their basements, and during heavy rains, sometimes their cars end up floating down the streets.

Some photos of Germantown during flooding look like things you’d imagine seeing in more coastal cities, like Miami or New Orleans:

East Germantown residents hope city offers flood bailout - WHYY
Germantown flash flood proved deadly as well as damaging - WHYY

But when you look at Germantown on a map, it’s hard to see why it’s a flood-prone area. It’s not in Southern Philadelphia, and the neighborhood doesn’t abut either the Schuylkill or Delaware Rivers. Germantown is in Northwest Philadelphia, far from the Delaware.

rabbi) alissa wise » map of philadelphia neighborhoods

The Schuylkill River borders the neighborhoods to the west of Germantown (Roxborough/Mayanunk), as seen by this map:

Philly H2O: Maps

So, given Germantown’s physical distance from the Schuylkill and Delaware Rivers, why is there flash flooding to the extent people are getting trapped in cars and Germantown basements get flooded with sewage on a semi-regular basis?

It becomes easier to understand when you look at a map of historic Philadelphia waterways.

Hidden Creeks | matthiasbaldwinpark

All those thin blue lines leading into the Delaware and the Schuylkill Rivers are tributaries. Upon the building of the city, the city planners wanted a flat, creek-free surface, so these tributaries were channeled underground via the sewer system. The valleys made by the tributaries were filled in to create the city.

The area where the young woman drowned in 2011 is where the Wingohocking Creek, a tributary to the Frankford Creek, which led to the Delaware River, once existed. Below is a picture of the sewer line designed to capture the waters of Wingohocking Creek; it is the largest sewer in the Philadelphia sewer system:

WHYY: History Explains East Germantown Flood |

When there are heavy rains, the sewers sometimes can’t take both the rainwater and the old waterways they contain. The sewers thus back up, causing flooded streets and sewage in home.

The flattening of the Wingohocking Creek bed had other consequences. A little over a couple of miles east of Germantown is Logan Triangle. In 1959, a series of explosions from a cracked gas main damaged a number of row houses. Smoke and fire drove people from their apartments. The gas line was repaired, but by 1986, the city could no longer ignore what was happening to the houses in Logan Triangle. There were more explosions. The houses were sinking into the ground. Ceilings were cracked. Walls buckled.

The reason why the gas main exploded in 1959 and the city ended up condemning and vacating houses after subsequent gas explosions in 1986 was because one of the original developers of the city filled in the Wingohocking Creek bed with cinder and ash; cinder and ash tend to wash away. Thus the houses, offices, roads, gas mains, everything lay upon shifting, eroding ground. Ultimately, by the year 2000, the city vacated and demolished almost a thousand properties that had become uninhabitable and dangerous.

In the first two decades of this century, Logan Triangle has been a 35-acre vacant lot, the site of a great deal of illegal dumping.

In 2018, the city has shifted Logan Triangle back into private hands for development. A developer plans to build a $25 million youth basketball complex on the site, with other supportive facilities, such as a library and computer lab. But because of the original problem of the ash fill over the creak bed, the developer would need to either remove the ash and replace it with more stable material or build structures that corkscrew into the ground to ensure stability.

How this issue of construction on uncertain foundations will be resolved is uncertain; at least as February 2020, the developer has yet to break ground on the project.

There is, however, this listing for apartments about a mile away from Logan Triangle. A one bedroom, one bath, can cost you north of $2200/mo. Before you sign a lease, you may want to inquire as to what’s up with the waters that once flowed down the Wingohocken Creek and whether or not those waters are adequately contained by the infrastructure.

The problem is that the more it rains, the more the area floods; the more the area floods, the more the ground is eroded away.

We’re not going to have a lessening of heavy rains anytime soon. It remains an open question as to how the city will manage to deal with the water the current sewer system has difficulty containing during periods of high rains.

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